Magnetic shielding for medical magnetic measurement

Abstract

The invention relates to a biomagnetic measurement device (1), comprising: - a support (2) which extends in a longitudinal direction (X) and is intended to receive the body of a patient (10); - a magnetically shielded enclosure (3) which extends in the longitudinal direction (X) and comprises an open end (31) facing the support (2); - magnetic sensors (7); - a sensor-holding system (4), which system is secured to the support (2) and is configured to hold the magnetic sensors (7) facing an organ of the body of the patient (10) in a position for acquiring biomagnetic signals; - a controller (5) which is connected to the sensor-holding system (4) via a cable (6), the cable (6) being configured to transmit an electrical signal and / or an optical signal to the magnetic sensors (7), the biomagnetic measurement device (1) being characterised in that the support (2) cannot move and the magnetically shielded enclosure (3) is mounted so that it can move in translation relative to the support (2) in the longitudinal direction (X) so as to be able to surround a portion of the support (2) from the open end (31), and in that a portion of the cable (6) which extends in the longitudinal direction (X) is secured to the support (2).

Description

[0001] Magnetic shielding for medical magnetic measurement

[0002] TECHNICAL FIELD

[0003] This disclosure relates to the general field of medical imaging devices based on the acquisition of magnetic signals of physiological processes in organs.

[0004] STATE OF THE ART

[0005] Various medical imaging devices exist to obtain a representation of physiological processes in organs such as the brain or heart. Some devices use electrodes placed on the body's surface to characterize the electrical currents flowing within the organ due to the resulting voltage differences across the body's surface. However, the propagation of electrical signals within the body is significantly disrupted at the interface between tissues with different resistivities or conductivities, for example, between bones and soft tissues, making the localization of the currents that created the measured voltages highly imprecise.

[0006] The use of magnetic signals provides more precise spatial information because, unlike electrical signals, magnetic signals are not subject to the aforementioned disturbances. However, the measured signals are of very low amplitude, on the order of femto-Tesla to pico-Tesla. It is therefore necessary to develop highly sensitive magnetic field sensors and to record the signals in a magnetically shielded enclosure to prevent interference from unwanted signals.

[0007] Most current medical imaging devices include a magnetically shielded enclosure with a volume of 15 to 50 m³ 3 The walls of the enclosure comprise several layers of materials with high magnetic permeability.

[0008] One type of sensor capable of achieving the necessary sensitivities is a superconducting magnetometer (known as a SQUID, an acronym for "superconducting quantum interference device"). These sensors require a massive shielded enclosure. This enclosure must contain the patient and sensors arranged within a large container filled with a cryogenic fluid, as well as a significant thickness of insulation to thermally separate the patient from the container.

[0009] A second type of sensor involves optically pumped atomic gases (or OPMs for "Optically Pumped Magnetometers"). This type of sensor allows for measurements with similar sensitivity to the first type of sensor, without the use of cryogenic fluid. It is then possible to use a smaller shielded enclosure, on the order of 1 to 5 m³. 3, for example a magnetically shielded enclosure such as that proposed by US 2019 / 0387647. However, these enclosures are expensive, impractical for an operator to use, and uncomfortable for the patient.

[0010] Alternatively, a cylindrical shielded chamber can be used, into which the patient is placed in a supine position, as proposed in US 2023 / 0204688 A1, or in A. Borna et al., “A 20-channel magnetoencephalography system based on optically pumped magnetometers” Phys. Med. Biol., vol. 62, no. 23, pp. 8909-8923, Nov. 2017. The associated measurement devices are more flexible, less expensive, and placed directly on the patient's body surface.

[0011] In such devices, the patient typically lies on a mobile support. The sensors are usually positioned on the patient by an operator, near the organ to be observed, before the mobile support is inserted into the cylindrical shielded enclosure. This causes discomfort for the patient. Furthermore, this operating method is impractical and presents an increased risk of sensor failure. Indeed, moving the mobile support and the patient equipped with the sensors can damage the cables connecting the sensor to the processing unit and its associated interface. To improve patient comfort, it is advantageous to reduce the weight of the sensors placed on the patient's body. Therefore, it is preferable to use lightweight cables specifically developed for medical applications, which are thinner and thus more fragile. This further increases the risk of failure.Furthermore, the positioning of the sensors may be altered during the movement, resulting in a degradation of the quality of the signals obtained in the measurement.

[0012] DESCRIPTION OF THE INVENTION

[0013] One purpose of this disclosure is to propose a compact and comfortable device for acquiring biomagnetic signals from a patient's organ, allowing for simple and precise placement of biomagnetic sensors opposite the organ, limiting the risks of biomagnetic sensor failure.

[0014] This goal is achieved using a biomagnetic measurement device comprising:

[0015] - a support extending along a longitudinal direction and intended to receive the body of a patient,

[0016] - a magnetically shielded enclosure extending along the longitudinal direction and comprising an open end opposite the support,

[0017] - magnetic sensors, - a sensor retention system, attached to the support and configured to hold the magnetic sensors opposite an organ of the patient's body in a position for acquiring biomagnetic signals,

[0018] - a controller connected to the sensor holding system by a cable, the cable being configured to transmit an electrical and / or optical signal to the magnetic sensors, the biomagnetic measuring device being characterized in that the support is immobile and the magnetically shielded enclosure is mounted movable in translation relative to the support in the longitudinal direction, so as to be able to surround a part of the support from the open end, and in that a portion of the cable extending in the longitudinal direction is fixed to the support.

[0019] The proposed device magnetically isolates the patient organ from which biomagnetic signals are to be acquired. This is achieved by sliding the magnetically shielded enclosure towards the organ after the magnetic sensors have been installed on the sensor support system. The patient's position remains stationary during setup and data acquisition, thus increasing patient comfort. Furthermore, once the sensor support system is in the acquisition position, it remains fixed. This minimizes the risk of strain or twisting on the cables connecting the sensors to the device's control system or human-machine interface, which could damage the cables.Indeed, it is advantageous to use lighter, and therefore thinner and more fragile, cables to connect the sensor positioned opposite the patient's organ to the controller, particularly for transmitting biomagnetic signals and ensuring the sensors function. Furthermore, the cable can include an optical fiber, as is commonly used in OPM-type magnetometers, which is less resistant to twisting. This also prevents the sensors from shifting relative to the patient to a less suitable position, thus avoiding degradation of the biomagnetic signals.

[0020] The biomagnetic measuring device may have the following advantageous and non-limiting characteristics, taken alone or in any technically feasible combination:

[0021] - the cable includes an optical fiber;

[0022] - the controller is further configured to: calculate a quality indicator of biomagnetic signals delivered by the magnetic sensors; compare the quality indicator to a threshold; and if the quality indicator is greater than the threshold, command an additional translation of the magnetically shielded enclosure relative to the support in the longitudinal direction;

[0023] - the sensor holding system includes a positioning mechanism in the position for acquiring biomagnetic signals;

[0024] - the positioning mechanism includes a joint allowing a translational movement of the sensor holding system relative to the support in the longitudinal direction, with a travel between 0.5 cm and 50 cm, preferably less than 25 cm;

[0025] - The positioning mechanism includes a joint allowing rotational movement of the sensor holding system around the longitudinal direction, with a range of motion between 1° and 45° 0 , preferably less than 20°;

[0026] - the positioning mechanism includes a clamping device configured to exert pressure in the direction of the patient's body organ, so as to keep the sensors pressed against the patient's body organ;

[0027] - the magnetic sensor holding system is an optically pumped magnetometer holding system;

[0028] - the patient's organ is the patient's brain;

[0029] - the device further includes a control device configured to control a translation of the magnetically shielded enclosure relative to the support in the longitudinal direction, so that the magnetically shielded enclosure moves from an installation position in which the magnetically shielded enclosure does not surround the sensor holding system to a magnetic isolation position in which the shielded enclosure surrounds the sensor holding system;

[0030] - the magnetically shielded enclosure is a telescopic enclosure comprising a plurality of concentric enclosures mounted movably in translation relative to the support along the longitudinal direction;

[0031] - the support includes an external enclosure extending along the longitudinal direction concentrically to the magnetically shielded enclosure, configured to receive the magnetically shielded enclosure when the sensor holding system is not in the position for acquiring biomagnetic signals;

[0032] - The device further includes a projection system configured to project an image inside the magnetically shielded enclosure. According to another aspect, a method for acquiring biomagnetic signals using the previously described biomagnetic measurement device is proposed, comprising the following steps:

[0033] - positioning of the patient's body on the support, the magnetically shielded enclosure being in an installation position in which it does not surround the sensor holding system;

[0034] - positioning of the sensor holding system in the position for acquiring biomagnetic signals opposite the patient's body organ;

[0035] - translation of the magnetically shielded enclosure along the longitudinal direction from the installation position to a magnetic isolation position, in which the magnetically shielded enclosure surrounds the sensor holding system;

[0036] - Acquisition of biomagnetic signals by magnetic sensors.

[0037] DESCRIPTION OF THE FIGURES

[0038] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0039] [Fig. 1] Figure 1 schematically illustrates a biomagnetic measurement device according to a first embodiment, in an installation position.

[0040] [Fig. 2] Figure 2 schematically illustrates the biomagnetic measurement device according to the first embodiment, in a magnetic isolation position.

[0041] [Fig. 3] Figure 3 schematically illustrates a biomagnetic measurement device according to a second embodiment, before patient installation.

[0042] [Fig. 4] Figure 4 schematically illustrates a sensor retention system for magnetoencephalography.

[0043] [Fig. 5] Figure 5 is a flowchart of steps of a method for acquiring biomagnetic signals, according to another aspect of the invention.

[0044] Across all figures, similar elements bear identical references.

[0045] DETAILED DESCRIPTION OF THE INVENTION

[0046] With reference to Figure 1, the biomagnetic measuring device 1 according to the present invention comprises a fixed support 2, a magnetically shielded enclosure 3, and magnetic sensors held by a sensor retention system 4. Support

[0047] The support 2 extends along a longitudinal direction along the X-axis and is designed to receive the body of a patient 10. In the embodiments shown in Figures 1 and 3, the patient 10 is intended to lie on the support 2, or in other words, the support 2 is designed to receive the body of a patient 10 in a supine position. The support 2 generally comprises a surface 21 extending along the substantially horizontal X-axis. The surface 21 of the support 2 is preferably ergonomically designed so that the patient lies comfortably. For example, the surface 21 is covered by a thin mattress. The surface 21 on which the patient lies can be flat or curved, as illustrated in Figure 3.

[0048] During the use of the device, particularly during patient setup or the acquisition of biomagnetic signals, the support 2 is fixed, i.e., immobile.

[0049] Magnetically shielded enclosure

[0050] The magnetically shielded enclosure 3 extends along the longitudinal direction X and includes an open end 31 facing the support 2, i.e., oriented towards the support 2, for example in a plane orthogonal to the X-axis. The magnetically shielded enclosure 3 may have a cylindrical shape, for example, be a cylinder open at its base (Figure 3). Alternatively, the shielded enclosure may have the shape of an open parallelepiped or, more generally, a polygonal prism open at one of its bases, or having an opening at both ends (Figure 1).

[0051] The magnetically shielded enclosure 3 is mounted to move in translation relative to the support 2 along the longitudinal direction X. This allows the magnetically shielded enclosure 3 to be able to surround part of the support 2 from the open end 31, when an operator wishes to acquire biomagnetic signals from an organ of the patient 10. In other words, the magnetically shielded enclosure 3 is movable so as to be able to expose most of the body of the patient 10 at the beginning and end of the examination, and then to be able to slide along the X axis by the open end 31 so as to cover the body of the patient 10 at least in part, and reduce measurement disturbances during the medical examination.

[0052] This also allows patient 10 to sit comfortably on support 2, without being hindered by the presence of the magnetically shielded enclosure 3, and in particular facilitates obtaining biomagnetic measurements for patients with reduced mobility. Furthermore, once positioned at the start of the examination, the patient does not move. Preferably, the position of the magnetically shielded enclosure 3 during the acquisition is adapted to the type of examination being performed. In particular, as illustrated in Figure 2, the magnetically shielded enclosure 3 does not necessarily completely cover support 2 and patient 10. This can reduce feelings of claustrophobia during the acquisition and further increase patient 10's comfort.

[0053] The magnetically shielded enclosure 3 is a magnetic shield. It typically comprises at least two layers of highly permeable material arranged concentrically around the X-axis. For example, the magnetically shielded enclosure 3 includes a layer of metallic alloy, such as mu-metal or permalloy. This is referred to as "passive" shielding. Preferably, the magnetically shielded enclosure 3 also includes a layer of a highly conductive but low-permeability metallic material such as copper or aluminum. Increasing the number of layers advantageously reduces noise in biomagnetic measurements performed by sensors held in the acquisition position.

[0054] It is important to note that these magnetic shields made of highly permeable materials must be distinguished from the much more common electrical shields, such as Faraday cages, or shields designed to attenuate electromagnetic or ionizing radiation. These other shields are made of materials with high electrical conductivity and do not need to be made of materials with high magnetic permeability.

[0055] Alternatively or in addition, the magnetically shielded enclosure 3 includes active shielding. "Active" shielding is defined as shielding achieved through a set of sensors and magnetic coils, configured to reduce some of the residual magnetic noise inside the magnetically shielded enclosure 3. More specifically, the magnetic coils can be controlled to attenuate the magnetic noise measured by the associated sensors.

[0056] Sensor retention system

[0057] The sensor holding system 4 is integral with the support 2. For example, it includes one end rigidly fixed to the support 2. The sensor holding system 4 is configured to hold magnetic sensors opposite a body organ of the patient 10 in a position for acquiring biomagnetic signals. In other words, the sensor holding system 4 is typically intended to be equipped with one or more sensors, for example, a plurality of OPM-type magnetometers, which are positioned on the body of the patient 10. The possible translational movement of the magnetically shielded enclosure 3 relative to the support 2 allows for easy positioning of the sensor holding system opposite the patient 10. Indeed, the operator, for example, a healthcare professional, can install the biomagnetic sensors on the sensor holding system 4 without being hindered by the magnetically shielded enclosure 3.The operator has access to the patient's body 10, and can easily manipulate the biomagnetic sensors to position the sensor holding system 4 in an optimal acquisition position.

[0058] More specifically, as illustrated in Figure 1, the magnetically shielded enclosure can be in an installation position in which it does not surround the sensor holding system 4. After translation of the magnetically shielded enclosure 3 along the X axis, towards the patient 10, the magnetically shielded enclosure 3 can be in a magnetic isolation position, in which the magnetically shielded enclosure 3 surrounds the sensor holding system 4, as illustrated in Figure 2.

[0059] Biomagnetic controller and sensors

[0060] The biomagnetic measuring device 1 further includes a controller 5 connected to the sensor holding system 4 by a cable 6 configured to transmit a signal to the magnetic sensors, for example, an electrical and / or an optical signal. In particular, the cable 6 can be configured to transmit an optical signal, for example, laser radiation, to a magnetic sensor. The cable 6 can also be configured to electrically connect the sensor to the controller 5, for example, to power magnetic field generating coils or to power a plasma excitation circuit in the sensor's gas cell, and to transmit to the controller 5 biomagnetic signals acquired by the sensor, for example, by a photodiode of the sensor.

[0061] Each magnetic sensor is therefore preferably connected by a cable 6 to the controller 5, the cables 6 being able to be gathered together in a sheath.

[0062] Controller 5 is a sensor control system. It is advantageously attached to support 2. For example, controller 5 includes a human-machine interface, allowing the operator to initiate the acquisition of biomagnetic signals. Preferably, controller 5 can command the movement of the sensor holding system 4 around the acquisition position.

[0063] The biomagnetic measuring device 1 has the particularity that a portion of the cable 6 extending along the longitudinal direction X is fixed to the support 2. For example, a portion of the cable 6 can be fixed to the surface 21 of the support 2, or to a wall of the support 2. Alternatively or complementaryly, a portion of the cable 6 can be fixed inside the support 2.

[0064] Typically, each sensor held to the sensor holding system 4 is connected to the controller by a cable 6. Preferably, each cable 6 is fixed to the support 2 over most of its length along an axis substantially parallel to the X-axis of sliding of the magnetically shielded enclosure 3. The plurality of cables 6 may be gathered into a common sheath.

[0065] Securing a portion of cable 6 reduces the range of movement possible for cable 6, and therefore reduces the risk of potential damage. Specifically, cable 6 is not subjected to mechanical stress during the translational movement of the magnetically shielded enclosure 3 relative to the support 2. This reduces the risk of device failures related to cable 6.

[0066] For example, the controller 5 may include an electronic system, and optionally an optical system, for operating an OPM-type magnetic sensor, i.e., an optically pumped magnetometer. The biomagnetic measuring device 1 typically has a dynamic range between -250 nT and +250 nT, preferably between -50 nT and +50 nT. Advantageously, the magnetic field amplitude is less than 50 nT. The use of low-amplitude magnetic fields reduces measurement errors due to involuntary patient movement, for example. Thus, it is possible to acquire biomagnetic signals with high accuracy. The controller 5 can monitor the acquired biomagnetic signals in real time.

[0067] In this embodiment, the sensor may comprise a cell containing an atomic gas, for example, helium in the form of a plasma, which allows certain helium atoms to be brought to their first excited state. In another example, the cell may contain rubidium atoms in their ground state. The optical system includes a laser configured to emit radiation passing through the sensor cell, tuned to a specific atomic absorption line. A magnetic field in several directions is applied by a system of coils, for example, Helmholtz coils, powered by current via cable 6. A photodiode can capture information relating to reflected radiation that has made a double pass through the cell, which is transmitted to the controller 5 via cable 6.The information is processed by the controller 5 to determine a measurement of the weak magnetic fields emanating from the patient's brain 10. The laser radiation can be transmitted from a laser source to the sensor via an optical fiber, for example, an optical fiber maintaining the polarization of the laser radiation. As explained previously, the cable 6 can include both electrical wires for transmitting the electrical signals from the sensor, for example, from the photodiode, corresponding to biomagnetic signals, and an optical fiber held in a sheath for transmitting the radiation from the optical system. In some embodiments, the cable 6 does not include an optical fiber. The cable 6 can also include electrical wires for supplying current to means for exciting the gas contained in the sensor cell.

[0068] To improve patient comfort, particularly when using the biomagnetic measurement device to measure brain signals, it is preferable to use the lightest possible cables. This reduces the weight exerted on patient when the sensors are held in the biomagnetic signal acquisition position. Preferably, the cable consists of pico-coaxial wires with a diameter of less than one millimeter. For example, each magnetic sensor is connected to a cable consisting of a sheath surrounding six pico-coaxial wires and an optical fiber. Alternatively, the cable may consist of a printed cable with planar conductive traces. Such cables are very fragile, even with the sheath.

[0069] Furthermore, optical fiber is fragile and more susceptible to damage than standard copper wires. It is best to avoid twisting or bending optical fiber cables, especially to maintain a slight bend in the cable at all times.

[0070] Thus, in practice, for OPM-type magnetic sensors, it has been observed that the cables 6 are one of the main sources of failure. Therefore, it is particularly advantageous to maintain the cable 6 rigidly during the use of the biomagnetic measurement device 1. More generally, this allows the use of thinner and shorter cables 6, and thus reduces the weight borne by the patient 10 during the acquisition of biomagnetic signals. Furthermore, since the weight of the cable 6 is primarily supported by the bracket 2, it is also possible to use more reinforced cables 6 to increase the durability of the biomagnetic measurement device 1 without reducing the comfort of the patient 10.

[0071] Positioning of the magnetically shielded enclosure

[0072] Preferably, the translational movement of the magnetically shielded enclosure 3 is achieved by a sliding mechanism that does not induce strong vibrations or mechanical stresses on the highly permeable material layers. Thus, the biomagnetic measuring device 1 is not degraded by repeated use.

[0073] The sliding mechanism includes, for example, a slider, that is, a guide piece for the magnetically shielded enclosure 3 in the longitudinal direction. For example, as illustrated in Figure 1, the support 2 may include a rail forming a slide, and the sliding mechanism for the magnetically shielded enclosure 3 includes a plurality of wheels or rollers arranged in the rail. For example, as illustrated in Figure 3, the support 2 may include a rod or a cylindrical portion, and the sliding mechanism for the magnetically shielded enclosure 3 includes a ring for sliding on the rod.

[0074] The translational movement can be induced manually by the operator, for example by means of a crank or a handwheel connected to the sliding mechanism.

[0075] Preferably, the translational movement can be automatically controlled. Typically, the biomagnetic measuring device 1 then includes a control device configured to control the sliding mechanism and generate a translation of the magnetically shielded enclosure 3 relative to the support 2 in the longitudinal direction X. The controlled sliding mechanism may, for example, include a pneumatic system with cylinders. For example, the control device may include two push buttons; pressing the first button causes the magnetically shielded enclosure 3 to translate in the longitudinal direction, and pressing the second button causes the magnetically shielded enclosure 3 to translate in the opposite direction, so as to return it to the installation position as illustrated in Figure 1.

[0076] As explained previously, the control device allows the magnetically shielded enclosure 3 to move from an installation position in which the magnetically shielded enclosure 3 does not surround the sensor holding system to a magnetic isolation position in which the magnetically shielded enclosure 3 surrounds the sensor holding system 4.

[0077] The control device can be integrated into the controller 5. The operator can thus control both the movement of the magnetically shielded enclosure 3 and the acquisition of biomagnetic signals.

[0078] Advantageously, the position of the magnetically shielded enclosure 3 can be controlled based on a biomagnetic signal quality indicator. In this case, the controller is further configured to: calculate the biomagnetic signal quality indicator delivered by the magnetic sensors; compare the quality indicator to a threshold; and when the quality indicator is above the threshold, command an additional translation of the magnetically shielded enclosure 3 relative to the support 2 along the longitudinal direction X.

[0079] This prevents excessive coverage of the patient's body. If the quality indicator is below the threshold, then the quality of the biomagnetic signals is sufficient. The sensors are therefore well positioned. Conversely, if the quality indicator is above the threshold, this may mean there is significant noise, and that the organ in the patient's body from which magnetic signals are acquired is not sufficiently magnetically shielded. Moving the magnetically shielded enclosure 3 allows for coverage of a larger portion of the patient's body 10, thus improving the quality of the measurements.

[0080] Typically, the quality indicator can be a noise indicator, corresponding, for example, to a standard deviation of the filtered signal in an appropriate frequency band, for example, a frequency range from 5 Hz to 80 Hz by removing a narrow band of frequencies around 50 Hz. The quality indicator can, as another example, correspond to a signal-to-noise ratio (or SNR), around the alpha rhythm of brain signals from patient 10 (8 Hz to 12.5 Hz), measured when patient 10 has their eyes closed.

[0081] For example, if the quality indicator is a noise figure, the threshold could be 40 fT / Hz over the 5 Hz to 80 Hz bandwidth, or if the quality indicator is a standard deviation of the noise, the threshold could be between 350 fT and 800 fT. Preferably, the threshold choice takes into account background noise from the brain, heartbeats, and blinks. In the example where the quality indicator is a signal-to-noise ratio over the alpha rhythm, the threshold could be between 2 and 5, typically 3.

[0082] Preferably, the magnetically shielded enclosure 3 is a telescopic enclosure comprising a plurality of concentric enclosures mounted to move in translation relative to the support 2 along the longitudinal direction X. According to the sliding principle described previously, the magnetically shielded enclosure 3 can be formed by several concentric layers of similar but not exactly equal diameter, the layers being able to slide relative to each other telescopically. This advantageously allows for a more compact biomagnetic measuring device 1. Indeed, the telescopic enclosure can cover a significant length of the patient's body 10 by sliding in shorter spaces. This reduces the overall size of the device 1 along the longitudinal direction (by increasing its thickness).It may also be simpler to move shorter segments of shielding, each segment constituting the magnetically shielded enclosure 3 being lighter.

[0083] Preferably, the support 2 includes an external enclosure 22, concentric with the magnetically shielded enclosure 3. As illustrated in the embodiment of Figure 3, the external enclosure 22 can extend along the longitudinal direction X concentrically with the magnetically shielded enclosure. The external enclosure 22 is configured to receive the magnetically shielded enclosure 3 when the sensor holding system 4 is not in the biomagnetic signal acquisition position, typically before the patient 10 is placed on the support 2. This allows, in particular, for the attachment of a human-machine interface for the controller 5, and also provides sufficient space for the installation of the device 1.

[0084] Positioning of the sensor mounting system

[0085] In one embodiment, the support 2 may include a sensor attached to the support 2. For example, OPM type magnetic sensors may be made attached to the support 2, via the sensor holding system 4. In this case, the sensor holding system 4 is mounted on the stationary support 2, in the acquisition position.

[0086] Preferably, the sensor holding system 4 includes a positioning mechanism for the biomagnetic signal acquisition position. This allows the acquisition position to be adjusted according to the patient's morphology 10, for example their height or build, or according to the organ on which measurements are to be acquired.

[0087] Typically, the positioning mechanism includes a joint allowing translational movement of the sensor holding system 4 relative to the support along the longitudinal direction X. This allows the sensor holding system 4 to be moved closer to or further from the patient's body 10, and allows the sensor to be installed in the acquisition position on the patient's body 10 at the start of the examination.

[0088] Preferably, the translational movement is possible with a travel between 0.5 cm and 50 cm, preferably less than 25 cm. The small travel of the sensor holding system 4 ensures fewer failures of the biomagnetic measuring device 1. Indeed, this allows the cable 6, which connects the sensor to the controller 5, to be subjected to minimal tension and only very slight deformations during the examination. The joint can also allow translation of the sensor holding system 4 relative to the support in another direction, for example, in a direction orthogonal to the longitudinal direction X.

[0089] Preferably, the positioning mechanism includes a joint allowing rotation of the sensor holding system 4 around the longitudinal direction. This allows the sensors to be oriented on the surface of the patient's body 10, typically ensuring that the sensors are oriented in a direction substantially orthogonal to the patient's body 10, opposite the organ of interest.

[0090] As before, the angular deflection is small, for example between 1° and 45°, preferably less than 20°. This prevents twisting of the cable 6 or reduces its radius of curvature when moving the sensor holding system 4 into the acquisition position. Preferably, the cable 6 includes a portion that is not fixed to the support 2, allowing sufficient length to perform the movements permitted by the positioning mechanism without exerting any twisting or tension on the cable 6.

[0091] Preferably, the positioning mechanism includes a clamping device configured to exert pressure in the direction of the patient's body organ 10, so as to keep the sensor pressed against the patient's body organ 10.

[0092] Typically, the clamping device may include tension springs, which can be released when the sensor holding system 4 is in the acquisition position. Alternatively, the clamping device may include air cushions, which are deflated and then inflated when the sensor holding system 4 is in the acquisition position.

[0093] Such devices allow the sensors to mechanically position themselves to conform to the shape of the patient's body 10.

[0094] Preferably, the biomagnetic measuring device 1 can be used at room temperature. It does not require a heating or cooling system. Preferably, to improve patient comfort 10, the device 1 may include an air conditioning or ventilation system configured to cool or ventilate the confined interior of the magnetically shielded enclosure 3 when patient 10 is positioned in the device 1. Alternatively or in addition, the device 1 may include a heating system configured to heat or cool the support 2 to improve patient comfort 10 when positioned on the support 2. In the embodiment where the biomagnetic measuring device 1 is used for magnetoencephalography, the magnetic sensor holding system 4 is an optically pumped magnetometer holding system, as described previously.

[0095] Such a device 1 can be used to measure biomagnetic signals representative of the brain activity of patient 10. In this context, the organ of patient 10 at which the sensors are held in the acquisition position is the head of patient 10.

[0096] Preferably, the device 1 includes a projection system configured to project an image inside the magnetically shielded enclosure 3. The projection system may include a projector located outside the enclosure 3, a screen located inside the magnetically shielded enclosure 3 opposite the patient, and a mirror for directing the projected image onto the screen. The projected image is intended to be viewed by the patient 10 when the patient 10 is positioned on the support 2 and the magnetically shielded enclosure is in a magnetically isolated position. The projected image may be controlled by the controller 5. This embodiment is particularly advantageous when the magnetically shielded enclosure 3 covers the upper part of the patient 10's body, especially their head, as is the case during magnetoencephalography.This allows for the transmission of information to patient 10 during the acquisition of biomagnetic signals, such as the remaining time. It also allows for the patient 10 to be entertained, thus improving their comfort and reducing their anxiety. Furthermore, it can stimulate patient 10's brain if the projected images correspond to specific stimuli.

[0097] Example of a sensor retention system 4

[0098] The sensor retention system 4 may include a helmet, intended to be placed on the patient's head 100. Referring to Figure 4, the sensor retention system 4 comprises a helmet 42 and an elastic clamping device 41, for example, as described in patent FR3100125. The sensor retention system 4 here includes two joints 44 allowing a sliding pivot connection with the support 2 forming a frame.

[0099] The headset 42 comprises a plurality of ports 43, each designed to receive a sensor 7, typically a magnetometer. The headset 42 is designed to hold a plurality of sensors 7, for example 64 sensors, in the acquisition position, 6 of which are schematically represented. The sensors 7 are arranged on the periphery of the headset 42 so as to acquire biomagnetic signals from the brain. Each sensor 7 can be connected to the controller 5 by a cable 6. The cables 6 are secured to the support 2 by a retaining system 61.

[0100] The sensors 7 can preferably automatically identify their relative positions with respect to each other. This is possible by local measurement of magnetic fields, from which the controller 5 can calculate the relative distances and orientations of the sensors on the flexible helmet.

[0101] The immobility of the support 2 ensures that the sensor holding system 4 is ideally positioned on the patient's head 100 and cannot shift to a suboptimal position when the patient 10 is covered by the magnetically shielded enclosure 3 for the examination. This guarantees the reproducibility of the measurement, as the position remains identical from one patient to another and from one examination to another.

[0102] Method for acquiring biomagnetic signals

[0103] With reference to Figure 5, a method for acquiring biomagnetic signals is then described, according to another aspect of the invention.

[0104] The process includes a step S1 of positioning the patient's body 10 on the support 2, the magnetically shielded enclosure being in the installation position P1 in which it does not surround the sensor holding system 4 (figure 1).

[0105] For example, initially patient 10 is completely outside the shielding. The patient then positions themselves, for example, on a bed, the axis of which is in line with the normal axis at the open end of the magnetically shielded enclosure 3. The absence of shielding around the body of patient 10 in step S1 allows patient 10 to get comfortable.

[0106] Once the patient is positioned, step S2 involves positioning the sensor holding system 4 in the biomagnetic signal acquisition position opposite the patient's body organ 10. The absence of shielding around the patient's body 10 in step S2 allows medical personnel to precisely position the sensors (placed, for example, on the helmet 5) on the patient's body 10, with complete freedom of movement to make this adjustment. Alternatively, the positioning of the sensor holding system 4 can be automatically controlled via the controller 5.

[0107] The magnetically shielded enclosure 3 can then move from the installation position P1 to the magnetic isolation position P2 by translating along the longitudinal direction X. In other words, the patient and the sensors with which they are equipped remain stationary, while, under the supervision of medical personnel, the magnetically shielded enclosure 3 slides along the axis orthogonal to its open end so as to cover a part of the patient's body, allowing the recording of their biomagnetic activity with significant attenuation of the surrounding magnetic field. The translation of the magnetically shielded enclosure 3 can be performed manually or controlled by the control device, which may be integrated into the controller 5.

[0108] Finally, an acquisition of biomagnetic signals by magnetic sensors can be carried out during an S4 step.

[0109] In a third phase, once the recording of biomagnetic signals is finalized, the magnetically shielded enclosure 3 can slide in the opposite direction to the translation carried out during step S3, so as to return to the installation position P1 where medical personnel can remove the sensors from the body of patient 10. Patient 10 can simply exit the device 1.

[0110] Method of using the device in an embodiment

[0111] The use of device 1 is described in detail here, in the embodiment illustrated in figure 3.

[0112] A horizontal support 2, for example a bed, allows patient 10 to comfortably lie down. The sensor support system 4 consists of a headset and / or various accessories (e.g., a headrest) containing OPM-type magnetic sensors. The sensor support system 4 is positioned in line with patient 10's position when lying down. The OPM sensor cables 6 pass through several openings in the support bed 2 and run under patient 10's body to their connection at the controller 5. The few tens of centimeters of cabling between the OPM sensor and the openings provide the necessary clearance for adjusting the headset 4.The helmet can be equipped with a joint allowing it to slide along the axis of the support bed 2 to rest on the patient's head 10, as well as joints allowing it to slide in other directions, for example perpendicular to the bed, to ensure close contact between the sensors and the patient's head. These joints are operated by a healthcare professional who ensures that the upper part of the helmet is positioned precisely in contact with the patient's scalp 10. Other adjustment mechanisms, including for example drawstrings and sliders, allow movement of the sensors radially to the patient's head 10, in order to precisely adjust the acquisition position to the patient's morphology.These other degrees of freedom are also adjusted by the healthcare professional so that all the sensors are in contact with the patient's head 10, thus allowing the capture of cerebral biomagnetic signals with optimal amplitude.

[0113] The cylindrical magnetically shielded enclosure 3 is formed by a plurality of concentric layers, for example, between two and five layers, typically three layers, of mu-metal. The magnetically shielded enclosure 3 is open at the end facing patient 10 and closed at the opposite end. Once patient 10 is positioned and the headset is optimally positioned and adjusted, the magnetically shielded enclosure 3 slides progressively along the longitudinal direction X, which is parallel to the axis of patient 10's body, from the installation position P1 to the magnetic isolation position P2, covering patient 10's body, or the part of the body, in this case the head, being examined. This movement is made possible by a rail mechanism attached to the magnetically shielded enclosure 3, sliding on ball bearings (or simply wheels) mounted on the support 2.The support bed 2 is fixed to the device 1 at one end, the other end of the support bed 2 resting on the inner surface of the magnetically shielded enclosure 3. In this case, a second rail and ball bearing mechanism ensures the sliding of the support bed 2 inside the magnetically shielded enclosure 3, the movement being driven by a flywheel meshed with a toothed wheel on a rack. The movement can also be driven by a chain drive or a pneumatic actuator. A force pressure sensor system ensures safe operation.

[0114] Once the magnetically shielded enclosure 3 has been moved to cover the patient's body 10, for example, up to the patient's waist, the healthcare professional checks on the controller's acquisition console 5 whether the signal quality indicator, reflecting, for example, the noise level, is satisfactory. If the quality indicator is below a threshold, the quality is sufficient, and the healthcare professional starts the acquisition directly. Otherwise, they continue to slide the magnetically shielded enclosure 3 to cover the patient's body 10 until the quality indicator value is below the threshold. For example, the healthcare professional commands the magnetically shielded enclosure to move down to the patient's knees before starting the biomagnetic signal acquisition.

[0115] Once the acquisition of biomagnetic signals is finalized, the healthcare professional slides the magnetically shielded enclosure 3 back in the opposite direction, for example to the installation position P1, so that once the translation movement is finalized, the healthcare professional can loosen the cord systems and slide the headset 4 to remove it from the patient's head 10. Once this is done, the patient 10 can get up from the support bed 2.

[0116] It will be understood that the embodiment described above considers a simplified configuration of device 1, in which the magnetically shielded enclosure 3 is open on the patient-side end.

[0117] Without departing from the scope of the invention, it is possible to use specific doors, attached or not to the magnetically shielded enclosure 3 at both ends. In this case, the first door, located at the end on the patient side, has an opening to allow the patient's body 10 to pass through. Closing the first door reduces noise during the acquisition of biomagnetic signals. The second door, at the opposite end, remains closed during the examination. It can nevertheless be opened during step S1 of patient 10 setup or step S2 of sensor support system 4 positioning, to allow the healthcare professional to adjust the joints, particularly on the patient's head 100. The second door can also have openings used if additional equipment is used during the examination and / or to add attachments to the support 2.

[0118] The description above primarily considers biomagnetic signal measurements where magnetometers are placed on the patient's head 100. However, the proposed device 1 also allows for the examination of other parts of the patient's body 10. In this case, the patient 10 can be positioned on the support 2 in the opposite direction, for example, with their feet facing the open end of the magnetically shielded enclosure 3.

[0119] Furthermore, both ends of the magnetically shielded enclosure 3 can be opened to magnetically isolate only the part of the body on which biomagnetic signals are to be measured. For example, device 1 can be used to acquire biomagnetic signals from the brain (in the process called magnetoencephalography), the heart (magnetocardiography), or the nerves (magnetomyography).

[0120] In the illustrated embodiments, the support 2 is intended to receive the body of a patient 10 lying down. However, in other embodiments, the patient may be intended to be positioned on the support 2 in a seated or standing position. The support 2 may then include a chair or an armchair, and the X-axis of translation is substantially vertical.

Claims

DEMANDS 1. Biomagnetic measuring device (1), comprising: - a support (2) extending along a longitudinal direction (X) and intended to receive a patient's body (10), - a magnetically shielded enclosure (3) extending along the longitudinal direction (X) and comprising an open end (31) opposite the support (2), - magnetic sensors (7), - a sensor holding system (4), attached to the support (2) and configured to hold the magnetic sensors (7) opposite an organ of the patient's body (10) in a position for acquiring biomagnetic signals, - a controller (5) connected to the sensor holding system (4) by a cable (6), the cable (6) being configured to transmit an electrical signal and / or an optical signal to the magnetic sensors (7), the biomagnetic measuring device (1) being characterized in that the support (2) is fixed and the magnetically shielded enclosure (3) is mounted movable in translation relative to the support (2) in the longitudinal direction (X), so as to be able to surround a part of the support (2) from the open end (31), and in that a portion of the cable (6) extending in the longitudinal direction (X) is fixed to the support (2).

2. Biomagnetic measuring device according to claim 1, wherein the controller (5) is further configured to: calculate a quality indicator of biomagnetic signals delivered by the magnetic sensors (7), the quality indicator being representative of a noise level; compare the quality indicator to a threshold; and if the quality indicator is above the threshold, command a translation of the magnetically shielded enclosure (3) relative to the support (2) in the longitudinal direction (X) so as to cover a larger part of the patient's body (10).

3. Biomagnetic measuring device according to any one of claims 1 and 2, wherein the sensor holding system (4) includes a positioning mechanism in the biomagnetic signal acquisition position.

4. Biomagnetic measuring device according to claim 3, wherein the positioning mechanism includes a joint allowing translational movement of the sensor holding system (4) relative to the support (2) in the longitudinal direction (X), with a travel between 0.5 cm and 50 cm, preferably less than 25 cm.

5. Biomagnetic measuring device according to any one of claims 3 and 4, wherein the positioning mechanism includes a joint allowing rotational movement of the sensor holding system (4) around the longitudinal direction (X), with a deflection between 1° and 45°, preferably less than 20°.

6. Biomagnetic measuring device according to any one of claims 3 to 5, wherein the positioning mechanism includes a clamping device configured to exert pressure in the direction of the patient's body organ (10), so as to keep the magnetic sensors (7) in contact with the patient's body organ (10).

7. Biomagnetic measuring device according to any one of claims 1 to 6, wherein the sensor holding system (4) is an optically pumped magnetometer holding system.

8. Biomagnetic measuring device according to claim 7, wherein the patient's organ (10) is the patient's brain (10).

9. Biomagnetic measuring device according to any one of claims 1 to 8, further comprising a control device configured to control a translation of the magnetically shielded enclosure (3) relative to the support (2) in the longitudinal direction (X), so that the magnetically shielded enclosure (3) moves from an installation position (P1) in which the magnetically shielded enclosure (3) does not surround the sensor holding system (4) to a magnetic isolation position (P2) in which the magnetically shielded enclosure (3) surrounds the sensor holding system (4).

10. A biomagnetic measuring device according to any one of claims 1 to 9, wherein the magnetically shielded enclosure (3) is a telescopic enclosure comprising a plurality of concentric enclosures mounted movable in translation relative to the support (2) along the longitudinal direction (X).

11. Biomagnetic measuring device according to any one of claims 1 to 10, wherein the support (2) comprises an external enclosure extending along the longitudinal direction (X) concentrically to the magnetically shielded enclosure (3), configured to receive the magnetically shielded enclosure (3) when the sensor holding system (4) is not in the biomagnetic signal acquisition position.

12. Biomagnetic measuring device according to any one of claims 1 to 11, further comprising a projection system configured to project an image inside the magnetically shielded enclosure (3).

13. A method for acquiring biomagnetic signals, using the biomagnetic measuring device (1) according to any one of claims 1 to 12, comprising the steps of: - positioning of the patient's body (10) on the support (2), the magnetically shielded enclosure (3) being in an installation position (P1) in which it does not surround the sensor holding system (4); - positioning of the sensor holding system (4) in the position for acquiring biomagnetic signals opposite the patient's body organ (10); - translation of the magnetically shielded enclosure (3) along the longitudinal direction (X) from the installation position (P1) to a magnetic isolation position (P2), in which the magnetically shielded enclosure (3) surrounds the sensor holding system (4); - acquisition of biomagnetic signals by magnetic sensors (7).

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